1. Field of the Invention
The present invention relates to a thermal transfer image-receiving sheet for a sticker and a method of manufacturing the same and in particular to a thermal transfer image-receiving sheet for a sticker which can prevent misregistering easily occurring in the thermal transfer image-receiving sheet in forming color printed images thereon and a method of manufacturing the same.
2. Description of the Related Art
In a general method for forming color printed images on a thermal transfer image-receiving sheet, a thermal transfer sheet having a color material layer consisting of 3 or 4 colors of yellow, magenta and cyan, and as necessary black alternately provided side by side thereon, and a thermal image-receiving sheet provided with a receptor layer as necessary, are first passed between a heating device and a platen roller pressed at certain pressure. Simultaneously, a heating portion of the heating device is selectively heated depending on information of an image to be printed, so a color material contained in the color material layer in the thermal transfer sheet is transferred to the thermal transfer image-receiving sheet or the receptor layer thereof to form a printed image. The thermal transfer sheet is provided with 3 or 4 colors subsequently, and thermal transfer process is repeated at several times to the same position in the thermal transfer image-receiving sheet whereby different colors are transferred and overlaid successively to form a color printed image thereon. In particular, thermal transfer of sublimation type is superior to thermal transfer of heat melting type in high resolution and multi-tone expression, and is used where high-quality printed images are required.
As one of such color printed image-forming systems, there is a system in which a color material layer on a thermal transfer sheet is overlaid over the whole surface for one picture on a thermal transfer image-receiving sheet, and the printed image of one picture is formed all at once. In this system, after a certain color is printed, the image-receiving sheet is reciprocated, while the thermal transfer sheet is wound in the moving direction to effect repeated printing on the same picture. By overlaying each color in this manner, a full color printed image is formed. The advantage of this system is that if positional accuracy is given, printed images are beautifully finished with a high printing speed due to the absence of overlaps between lines which appear in the serial system. However, this system has the disadvantages such as easy occurrence of so-called misregistering due to poor positional accuracy on a paper, difficulty in attaining the miniaturization, lightening and low price of printers therefor, and so on.
As printers used in the above-described systems, the following printers are known.
For example, a printer for reciprocating a thermal transfer image-receiving sheet by fastening one end of the sheet with a chucking member is excellent in convey accuracy because the sheet is reciprocated with the independent chuck member. However, a relatively large thermal transfer image-receiving sheet of e.g. A3 or more in size, which can though be easily printed, requires a large, mechanically complicated and expensive printer, with which a small thermal transfer image-receiving sheet is difficult to print.
A printer for reciprocating a thermal transfer image-receiving sheet by rotation of a platen roller provided thereon with a chucking member fixing one end of the sheet, suffers from the problem of failing to send the thermal transfer image-receiving sheet in order to discharge it.
A printer for reciprocating a thermal transfer image-receiving sheet by rotation of grip rollers consisting of a rubber roller and a metal roller for fixing one end of the sheet therebetween is used most widely at present because its simple structure enables miniaturization thus making the price of the printer low. The grip rollers in this printer consist of a rubber roller for preventing a paper from sliding and a metal roller having fine and thin spikes of about 40 to 100 .mu.m in height formed thereon by etching for conveying the paper accurately by biting it by the spikes. Originally, the grip rollers were used mainly in single-color printers such as those for blueprint diazo copy or drafting not requiring the reciprocating motion of a thermal transfer image-receiving sheet, and therefore, printers using the grip rollers are poor in convey accuracy and easily cause misregistering where the thermal transfer image-receiving sheet is reciprocated for printing. If the press between the rubber roller and the metal roller is increased, convey accuracy at the time of reciprocating motion is improved, but the spikes on the metal roller bite into the thermal transfer image-receiving sheet to leave spike marks on the sheet. These spike marks are a great problem particularly in the case where the thermal transfer sheet is thin, and some spike marks penetrate the thermal image-receiving sheet to reach the surface of the image-receiving face thereof, resulting in deterioration of the qualities of the printed product.
To solve the problem, there have been marketed thermal transfer image-receiving sheets adapted to various types of printers, in consideration of characteristics of commercial printers, such as convey accuracy of the printers, press between grip rollers, degree of spike marks occurring with increasing press between grip rollers, or the like. By way of example, such thermal transfer image-receiving sheets are thickened to prevent the influence of spikes on the image-receiving face even if the press between the grip rollers is increased to improve convey accuracy.
However, it significantly increases costs for development and manufacture to provide thermal transfer image-receiving sheet with specifications adapted to various types of printers. Further, thickening of thermal transfer sheets to reduce the effect of spikes can result not only in a limit to thickness and layer structure preferable for usual thermal transfer image-receiving sheets but also in a limit to usual functions of sheets, for example, characteristics such as texture, drape, luster etc.